Along with the development of high-brightness light emitting element, an LED light using LED as a light source is progressively used for an automobile rear lamp etc. LED offers a good visibility due to its sharp spectrum. Also, it has a high signaling speed to a following vehicle since the response speed is high, and it has a significant effect in reducing the braking distance in the case of high-speed driving. Further, since LED itself is a monochromatic light source, it is not necessary to cut light color other than desired color by using a filter as is the case with an electrical light bulb. Thus, it can be a monochromatic light source with high efficiency and can save energy.
FIG. 103 shows an example of the LED light. As shown in FIG. 103, a LED light 1000 uses, as a light source, a lens-type LED 1010 that a light emitting element 1020 is sealed with transparent epoxy resin 1050 while being formed of a convex lens. The lens-type LED 1010 is fabricated such that the light emitting element 1020 is mounted on a lead 1030a of a pair of leads 1030a, 1030b, the light emitting element 1020 is bonded to the lead 1030b through a wire 104, and the entire LED is sealed with transparent resin 1050 while being formed of a convex lens. A reflection mirror 1060 with paraboloid is disposed around the lens type LED 1010, and a Fresnel lens 1070 is disposed over the LED 1010. In the above composition, light to be radiated from the lens type LED 1010 is reflected by the reflection mirror 1060 or converged by the Fresnel lens 1070, and is all radiated upward nearly in parallel. Then, light is transmitted through a resin lens 1090 while being diffused by an uneven interface that is formed on the bottom surface of resin lens 1090, and is externally radiated having a diffusion angle of about 20 degrees to meet the regulation for vehicle rear lamp.
On the other hand, as the output of light emitting element is further enhanced, it is desired to cover a predetermined emission area by using a reduced number of light emitting element. This aims to reduce the number of parts and to save labor in mounting parts.
However, in the LED light 1000 described above, if it is tried to use one light emitting element to cover a large area, its dimension increases at a homothetic ratio both in the width direction and in the depth direction. Further, if it is tried to forcedly make it low-profile, its appearance is spoiled. Therefore, there is a problem that it is difficult to provide a low-profile light source which is a characteristic of LED. In addition, light not heading from the light emitting element 1020 to the reflection mirror 1060 or Fresnel lens 1070 cannot be optically controlled and cannot be, therefore, externally radiated. Thus, there is a further problem in external radiation efficiency.
To solve these problems, Japanese patent application laid-open No. 2001-93312 discloses an LED light.
FIG. 104 shows the LED light disclosed therein. FIG. 104 (a) is a cross sectional view showing the LED light with a light source centered. FIG. 104(b) is a perspective view showing part of the LED light. The LED light is composed of: the light source 1100; a first reflection surface 1110 that is disposed at a position on the center axis of light source 1100 while being opposite to the light source 1100 and that has a parabolic reflection surface 1110a to allow light radiated from the light source 1100 to be reflected in the Y direction nearly orthogonal to the center axis X of light source 1100; and a second reflection surface 1120 that is disposed around the first reflection surface 1110 and that has a plurality of reflection facets 1120a to allow light reflected by the first reflection surface 1110 to be reflected in the direction of center axis X. In this composition, light to be radiated from the light source 1100 is reflected in the Y direction by the parabolic reflection surface 1110a of first reflection surface 1110, and then the reflected light is reflected in the direction of center axis X by the reflection facets 1120a of second reflection surface 1120. Thus, vehicle signaling light with a predetermined radiation angle can be radiated over a predetermined area.
However, in the LED light, there is a problem that light directly radiated from the light source 1100 cannot be taken out in the perpendicular direction because of being blocked by the first reflection surface 1110 disposed over the light source 1100 and, therefore, a dark portion is generated at the center.
To solve this problem, International Publication No. 99/09349 discloses an LED light.
FIG. 105 shows the LED light disclosed therein. FIG. 105(a) is a cross sectional view showing the LED light with a light source centered. FIG. 105(b) is a cross sectional view cut along the line K-K in FIG. 105(a). The LED light is composed of: a light source 1620 that has a light emitting element 1600, light emitting source, a dome section 1610 and a base section 1610A; a lens element 1740 that has an incident surface 1630, a first reflection region 1640, a first reflection surface 1640A, a direct transmitting region 1650, a second reflection region 1660, a radiation surface 1670, an edge 168, and posts 1720, 1730; and an optical element 1750 that pillow lenses 1750A are arrayed. The second reflection region 1660 of lens element 1740 has pairs of an extraction surface 1660A and a step down 1660B that are formed 360 degrees around the first reflection region 1640. Further, as shown in FIG. 105(b), the light source 1620 is composed such that the dome section 1610 is positioned at the center of first reflection region 1640 by fitting the posts 1720, 1730 of lens element 1740 into recesses 1620A, 1620B of the base section 1610A.
In this composition, light to be radiated from the light source 1620 is reflected by the first reflection surface 1640A in a direction orthogonal to the center axis of light source 1620. Then, reflected light is further reflected by the extraction surface 1660A in the center axis direction to be radiated as light A from the radiation surface 1670. On the other hand, light B from the light source 1620 is directly transmitted though the direct transmitting region 1650 to be radiated in the center axis direction. Thus, light with an enlarged radiation area is entered into the optical element 1750.
However, in the above LED light, there is a problem that the entire thickness must be increased since there is provided the dome section 1610 to converge light radiated from the light source 1620 to the center axis.
Further, it is difficult to perfectly align the center axis of lens element 1740 with the center axis of light source 1620 in fabrication and, therefore, a deviation in position may occur and uniformity in brightness is difficult to obtain over all directions. Namely, the light source 1620 and lens element 1740 are separately prepared and then aligned with each other in fabrication. If a precision in alignment of the center axis of light source 1620 with the first reflection region 1640 of lens element 1740 lowers, the amount of reflected light in all reflection directions given by the first reflection region 1640 becomes uneven and unevenness (difference) in brightness will occur on the surface of LED light. Especially in the case of optical system with such a high light focusing characteristic that most of light radiated from the light source 1620 is radiated upward, there occurs a significant difference in brightness due to unevenness in the light distribution of light source 1620 itself or due to unevenness in optical characteristics thereof caused by a deviation in position in a direction perpendicular to the center axis between the lens element 1740 and the light source 1620. Namely, in the above LED light, since light form the light emitting element 1600 is radiated being focused by the dome section 1610, there may occur a significant difference in the distribution of light to be radiated from the dome section 1610 even when a slight deviation in position is generated between the center axis of light source 1600 and the center axis of dome section 1610. As described above, it has a potential problem that the structure of light source 1620 itself may cause a difference in light distribution characteristic. In addition, due to a deviation in position in mounting the lens element 1740 separately prepared, there occurs a problem that the amount of reflected light in all reflection directions given by the first reflection region 1640 becomes uneven.
Further, there are problems that the light utilization efficiency lowers due to sideward light not enabled to be focused on the center axis by the dome section 1610 and that the radiation area cannot be therefore enlarged. Namely, light to be radiated from the light source 1620 in the horizontal direction (X direction) is reflected by the second reflection region 1660. Further, light not enabled to be reflected by neither the first reflection region 1640 nor the second reflection region 1660 is not radiated in the z direction. Thus, the light utilization efficiency lowers.
Further, since the light source 1620 and the lens element 1740 are prepared separately, light from the light source 1620 is transmitted through air layer before entering into the incident surface 1630 of lens element 1740. Therefore, loss of light is generated in that air layer or at the interface. If a stain exists at the interface of the light source 1620 and lens element 1740, further loss of light is generated. Still further, due to the separate preparation, a deviation in position may occur when being subjected to a physical shock. Therefore, it is difficult to design an optical system that the light emitting element and reflection mirror is close to each other. Further, there are problems that the number of parts or fabrication steps increases and that variation of precision in fabrication increases.
These problems described above are also included in the LED light disclosed in Japanese patent application laid-open No. 2001-93312.
Accordingly, even when a lamp such as an automobile brake lamp-integrated tail lamp is manufactured by using such LED lights, the proper brightness of light source cannot be utilized due to the above problems. Because of this, the lamp appears dark as a whole and lacks a degree of freedom in appearance.
An object of the invention is to provide a light emitting diode and an LED light that have a good appearance based on the low-profile property of LED, an enlarged radiation area while using one light emitting element, and an even brightness in all directions and high external radiation efficiency, and to provide a high-brightness lamp that is enabled to efficiently use light radiated from a light source.
Another object of the invention is to provide a light emitting unit that is low-profile, highly efficient and that can be applied to an irregular shape without reducing the efficiency and that can be disposed along a slope while having high external radiation efficiency.
A further object of the invention is to provide a lamp using a light emitting unit that is enabled to radiate light with an angle widened as much as possible while preventing the proper brightness of a light source.
A still further object of the invention is to provide a lamp that is low-profile, highly efficient, and that has a large degree of freedom in appearance and an even brightness on the entire surface and that offers a natural feel with glitter.